1. Field of the Invention
The present invention relates to a display device, and more particularly, to an organic electroluminescence display device with a high brightness and method for fabricating the same.
2. Discussion of the Related Art
Organic electroluminescence display devices are one type of self-emission display devices and do not require an additional backlight source, which is different from liquid crystal display (LCD) devices. Organic electroluminescence display devices have advantages of lightweight, a slim profile, a low voltage driving, a high light-emission efficiency, a wide viewing angle, a fast response time, etc. and are thus advantageous in realizing high quality moving pictures.
Organic electroluminescence display devices are generally fabricated by deposition and encapsulating processes and thus their fabrication process is simple compared with LCD devices or plasma display panels (PDP). Also, when an organic electroluminescence display device is driven by an active matrix driving method in which a thin film transistor (TFT) functions as a switching device in each pixel, a high definition and large-sized organic electroluminescence display device can be realized with a low power and high brightness.
An organic electroluminescence display device is generally formed by attaching a substrate having an array device and an organic light emitting diode (OLED) to an encapsulation substrate. Because the yield of the organic electroluminescence display device is determined by multiplying the yield of the array device and the yield of the OLED, the total process yield of the organic electroluminescence display device is greatly limited by an OLED fabrication process. For this reason, a dual panel type organic electroluminescence display device has been proposed in which the array device and the OLED are formed on different substrates.
FIGS. 1A and 1B are views of a dual panel type organic electroluminescence display device according to the related art. FIG. 1A is a circuit diagram of the organic electroluminescence display device, and FIG. 1B is a cross-sectional view of the organic electroluminescence display device.
Referring to FIGS. 1A and 1B, a plurality of gate lines 11 and data lines 21 are formed to cross each other on a substrate 10. The gate lines 11 and the data lines 21 define pixel regions P. Power lines 31 are formed parallel to the gate lines 11 and spaced from the gate lines 11 by a predetermined interval.
Each of the pixel regions P includes a switching TFT S-Tr connected with the gate lines 11 and the data lines 21, a driving TFT D-Tr connected with a drain electrode of the switching TFT S-Tr, a capacitor connected with a source electrode of the driving TFT D-Tr, and an OLED E electrically connected with a drain electrode 50b of the driving TFT D-Tr. The OLED E is formed on an upper substrate (not shown) spaced from the substrate 10 by a predetermined interval. The power line 31 electrically connects the source electrode 50a of the driving TFT D-Tr and is grounded to maintain a potential of the OLED E.
Because a gate insulating layer 30 is interposed between the power line 31 and the driving TFT D-Tr, an etching process is performed on the gate insulating layer 30 in order to electrically connect the power line 31 with the driving TFT D-Tr. However, a part of the power line 31 is also etched during the etching process, and thus the contact resistance between the driving TFT D-Tr and the power line 31 included in each pixel region increases, thereby generating a voltage drop in each pixel and degrading the brightness and uniformity of the organic electroluminescence display device. Also, because the power lines 31 are formed in the pixel regions, the effective area of the pixel region and the design area of the TFT are reduced.